Characterization of an acid-stable catalase KatB isolated from Bacillus altitudinis SYBC hb4

Abstract

In recent decades, many microorganisms have been selected and bred for industrial production of alkali-stable catalases. Given the diversity and excellent properties of Bacillus catalases, the aim of this work was to screen potent acid-stable catalases from Bacillus strain(s). A strain with higher production of catalase activity was identified and designated as Bacillus altitudinis SYBC hb4 based on phenotypic properties, 16S rRNA and gyrB gene analyses. Its four catalase genes were cloned successfully and designated as katX, katB, katN1 and katN2, respectively. Three distinct catalases were detected by isozyme zymography; however, only one (KatB) was successfully identified by MALDI-TOF. KatB had an estimated molecular mass of 228 kDa, and consisted of four identical subunits of 57 kDa. KatB displayed optimal activity under conditions of pH 5.0, 30 °C and 25 mM H2O2. The apparent Km and Vmax were calculated to be 62 mM and 33.4 mol min−1 mg−1, respectively. KatB can maintain at least 60 % relative activity after 6 h under conditions of pH 5.0 and 30 °C. Its activity and stability were higher compared to bovine liver catalase under slightly acid conditions (pH 5.0). Thus, B. altitudinis SYBC hb4 KatB might represent a potential acid-stable catalase used in acidic conditions.